Characterization of DEB powders and pellets for CA/CaCr04 thermal batteries

A detailed characterization study was conducted of catholyte or depolarizer-electrolyte-binder (DEB) mixes used in Ca/CaCrO4 thermal batteries. A number of the physical and chemical properties of powders and pellets of the DEB mixes were examined for correlation to electrochemical performance in 5-cell and, to a lesser extent, single-cell batteries. Powder characteristics evaluated included: chemical composition, segregation, flowability, bulk density, and BET surface area. Pellet characteristics evaluated included: break strength, forming force, electrolyte leakage at 400C after 0.5 h, and deformation at 530C under an applied pressure of 71 kPa (10.3 psi). Three series of DEB mixes were formulated at constant D/E weight ratios of 0.50, 0.64, and 0.80 to study the effect of SiO2 binder at concentrations of 8 to 12 wt%. Three additional series of DEB mixes were formulated at constant E/B weight ratios of 4.5, 5.5, and 6.5 to study the effect of CaCrO4 depolarizer at concentrations of 30 to 40 wt%. The BET surface area and chemical composition of DEB powders, and the electrolyte leakage and deformation of DEB pellets, could be correlated to the activated lives and pulse characteristics of the 5-cell batteries built with these mixes.